who's the oldest?

[Inderjit Sanghera]

Bombadil seems to have been in Arda from the start the Ents seem to be the first race that entered Arda, Treebeard was the oldest of the 'Ents' as a race, whilst Tom was a individual a intentional enigma.

Even some whole inventions like the remarkable Ents, oldest of all living rational creatures

Letter #131; Letters of Tolkien

Ents the most ancient people surviving in the Third Age

Appendix F

When the children awake, then the thought of Yavanna should awake too, and it will summon spirits from afar and they will go among the kelvar and olvar

Of Ents and Eagles; HoME 11

We also find in the Treason of Isengard[/I (HoME 7) that the chapter [I]Treebeard was mainly written 'written itself' that it had no basis, Tolkien just wrote and followed his train of thoughts.

He is called 'eldest' or referred to as being the eldest creature by others, such as Gandalf and Celeborn.

Elves are the 'firstborn' of the Eruhini and the first speakers-hence the collective term 'Quendi'.